Energy absorbers may aid in preventing damage to vehicles, particularly in low speed collisions, such as at or below 5 mph. In one exemplary application, an energy absorber may be positioned in front of a bumper beam and behind a decorative fascia at the front or the rear of a motor vehicle. One such prior art energy absorber may comprise a combination of injection molded blocks with foam blocks interspersed between the injection molded blocks, attached to a bumper beam. FIGS. 1 and 1A illustrate such a construction.
Although such an energy absorber may be effective, the use of multiple separate components that must be assembled together may result in higher molding and tooling costs providing complexity. Assembling separate components to form an energy absorber may be a complex process and may require an excessive amount of labor. It may therefore be desirable to provide a molded energy absorber made of a tunable and lightweight material that only requires attachment to a bumper beam.
Additionally, vehicles may be of different weights and sizes which may further complicate the management of energy during an impact. Providing an energy absorber capable of effectively managing a 5 mph impact of a 2500 lb. car vs. effectively managing a 5 mph impact of a 3500 lb may result in quite different dimensional requirements. It would therefore be desirable to provide a single general energy absorber configuration that can be easily tuned to cover a wide range of vehicle sizes and weights without major geometry changes so that the amount of MVSS testing may be minimized.
The Federal Government mandates low speed vehicle testing and compliance under CMVSS 215 to provide vehicles that can undergo a low speed (5 mph or less) impact against a pole, another vehicle or other object without specific damage. CMVSS 215 is a Standard set up to test a front or rear bumper with a series of pendulum impacts followed by a 5 mph flat barrier impact. This standard only applies to passenger cars. NHTSA 581 is a Standard that establishes requirements for the impact resistance of vehicles in low speed front and rear collisions. It is intended to reduce physical damage to the front and rear ends of a passenger motor vehicle from low speed collisions. The test consists of a 5-hit pendulum series where the last impact is a 2.5 mph flat barrier.
More specifically, CMVSS 215 includes two longitudinal pendulum impacts at 5 mph (height between 16 and 20 inches), one corner high pendulum impact at 3 mph (pendulum impacts shall be spaced apart by at least 2 inches vertically or 12 inches horizontally) and a flat barrier conducted at 5 mph, the impacts done in series.
NHTSA (FMVSS) part 581 includes two longitudinal pendulum impacts at 2.5 mph (height between 16 and 20 inches), two corner pendulum impacts at 1.5 mph (pendulum impacts shall be spaced apart by at least 2 inches vertically or 12 inches horizontally) and a flat barrier conducted at 2.5 mph, the impacts done in series. Planer loads during an impact can not exceed 2000 lbs. No paint/finish separation is allowed. No fastener breakage is allowed.
Additional judgment criteria that apply to both standards after impact include that                lamps and reflectors are free of cracks        Headlamps are adjustable per part 108.1 and SAE J599        hood, trunk and doors operate normally        fuel and cooling systems operate normally with no leaks        the exhaust exhibits no leaks or constrictions, and        the propulsion, suspension, steering and braking all operate in normal manner.        